1. Field of the Invention
The present invention relates to a scroll fluid machine, which is used as a compressor, for example.
2. Description of the Related Art
Generally in the scroll fluid machine, deformation is caused in the wrap parts of a fixed scroll and an orbiting scroll due to compression heat of a fluid, so that the wrap parts of the fixed scroll and the orbiting scroll come into contact with each other to cause lowering of reliability due to abrasion and generation of noise.
JP-A No. 2003-97462 discloses a scroll fluid machine, which prevents contact by making smaller the wrap tooth thickness on the cooling air downstream side rising to a high temperature and largely deformed, and enlarging a clearance between the wrap parts.
JP-A No. 2008-51034 discloses a scroll fluid machine, in which an inner peripheral side groove, an outer peripheral groove and a communicating groove are formed in a sliding surface on the outer peripheral part of a fixed scroll with an orbiting scroll.
In the scroll fluid machine described in JP-A No. 2003-97462, since a flange of the fixed scroll is fastened to a casing, a fixed scroll end plate is bent due to thermal expansion and the wrap inclines inwards. This deformation is largest on the outermost peripheral side integrated with the flange, so machining for preventing contact between the wraps should be made larger as compared with the inner peripheral side. This machining is decided depending on the maximum deformation amount at the highest temperature when the compressor is continuously operated approximately at the maximum allowable working pressure. Consequently the clearance between the wraps is large in an operation mode in which the wraps do not reach the assumed highest temperature such as the operation immediately after starting of the compressor and the intermittent operation of repeating the operation and the stop, so that it is impossible to maintain the compression efficiency.
In the scroll fluid machine described in JP-A No. 2008-51034, a projecting part is not formed on the back of the inner peripheral side groove, an outer peripheral side groove and the communicating groove formed in the sliding surface of the outer peripheral part of the fixed scroll with the orbiting scroll. Consequently when the fixed scroll end plate is thermally expanded, deformation due to the thermal expansion cannot be absorbed in the flange part, so that the wrap inclines inwards to come into contact with a wrap part of the orbiting scroll. Therefore, in order to secure the reliability, for example, machining for preventing the wrap contact as in JP-A No. 2003-97462 is needed, and it is impossible to maintain the compression efficiency.
The present invention has been made in the light of the above problem and it is an object of the present invention to provide a scroll fluid machine, which is improved in reliability while the compression efficiency is maintained by preventing a fixed scroll and an orbiting scroll from coming into contact with each other without increasing a clearance between wrap parts of both scrolls.